Many applications are known from the prior art where an annular record carrier is rotated in correspondence with the passage of time, and wherein a sequence of events is recorded on the record carrier. Perhaps the most commonly known application is in a vehicle trip recorder which records the movements and/or stops of a vehicle throughout a certain period of time in correspondence with the passage of time. This is for instance common on commercial trucks and the like, in connection with machine tools or the like.
This type of apparatus utilizes annular record carriers of paper or the like on a surface of which a record of the sequence of events to be recorded, is traced. Such a recording has the advantage that all of the recording track is readily visible, that the record carriers can be inserted and removed from the apparatus quickly and with little difficulty, and that the recorded data are available immediately and with no problem, as opposed for example to the recording on strip-shaped record carriers with a location of a particular period in time - and of the incident recorded to have taken place in this period -- is much more difficult to locate.
Apparatus of this type usually has a housing composed of two sections which can be pivoted relative to one another between an open and a closed position, the purpose being to afford ready access to the record carrier for removal of a used one and installation of a new one. If the apparatus is a trip recorder for vehicles, then one of the housing sections usually includes various elements, for example a counter which counts the distance travelled by the vehicle through the elapsed time period, a drive for rotating the annular record carrier, a clockwork for indicating the elapsed time, means for indicating vehicle speeds, motor rpm and perhaps light sources for illuminating the apparatus.
In apparatus of the type in question the annular record carriers are clamped against a rotary support which is driven in correspondence with the passage of time and which has a spindle that extends through a center opening of the annular record carrier. A particular problem of this type of apparatus results from the manner in which the record carrier is clamped to the support, especially during the replacement of record carriers and their subsequent clamping in place. The replacement of one record carrier with another must be carried out with very great care because any damage to the record carrier during installation and/or removal, for example scratches, bends or the like, will substantially and disadvantageously influence the accuracy of the recordings which can be made on the record carrier, which is particularly bothersome if the recorded information is later to be read machanically or electronically.
Various proposals have been made for clamping the record carrier onto its support with which it rotates. All of these proposals have disadvantages of one type or another. For example, the clamping uni-directional tensioning of the record carrier, causing the same either to shift out of its center position or to be deformed transversely of its center position, so that in any case the later recording track will no longer be in proper correspondence with the elapsed time. Especially if such records are then subsequently read in mechanical or electrical readers, this will result in inaccurate evaluations.
Other prior-art proposals require that the annular record carrier be placed over a member which extends through the center opening of the record carrier and is subsequently used to clamp the same in place. This, also, has various disadvantages, including the fact that it is very difficult to avoid some damage to the portion of the record carrier which borders the center opening, thus allowing the record carrier to move off-center with reference to the spindle and again permitting an eccentric track to be scribed on the record carrier. Evidently, a reference to the danger of damage to the annular record carrier is being made because it is important to realize that in the applications where such record carriers are used, the record carriers are likely to be subjected to very rough handling. In complete contradistinction to this, the prior-art proposals provide apparatus wherein the record carriers must be handled with extreme care to avoid damage to them; this is of course a factor which totally disregards the environment in which the record carriers are employed.
Still other prior-art proposals also have disadvantages which either do not clamp the record carrier in place with sufficient accuracy and/or firmness to prevent shifting of the record carrier on its support and the subsequent scribing of an improper track, or which are of such a nature that relatively high frictional momets are transmitted to the drive, the support and hence the record carrier, thus causing damage to the drive over a period of time.